(1) Field of the Invention
The present invention relates to a communication system and a mobile wireless communication device which can communicate on a VoIP (Voice over IP) network, such as a mobile phone and the like, and especially to a technology for making an emergency call.
(2) Related Art
A conventional technology for making an emergency call by a telephone communication on the VoIP network (hereinafter, referred to as a “VoIP communication”) is disclosed in Japanese Published Patent Application No. 2003-198757.
The technology disclosed in Japanese Published Patent Application No. 2003-198757 is as follows. When a user makes an emergency call from an IP phone terminal via the VoIP network, an IP packet including location information of the user and a phone number of an emergency call destination, such as a police station, a fire station, and the like is sent to the VoIP network. Then, a connection with an emergency call facility in a predetermined area corresponding to the location information is established to start a conversation. This technology takes account of an immediacy problem in an emergency that the emergency call may not be able to be made to an emergency call facility in an appropriate area by the VoIP communication, because the phone number of the emergency call destination does not include information specifying an area.
There are two types of VoIP communications. One is transmission/reception of a voice packet on the Internet, and the other is transmission/reception of a voice packet on an IP network that is exclusively established by a communication carrier. In recent years, the number of users of the VoIP communication by the IP network offered by the communication carrier increases because the VoIP communication by the IP network has an advantage of a lower communication expense. If a user contracts with the communication carrier, the user can start a conversation by connecting to the IP network of the communication carrier. Also, not only a fixed-line phone which can perform the VoIP communication, but also a mobile terminal such as a mobile phone which can perform the VoIP communication has been proposed. By wirelessly connecting to an access point of the communication carrier to which the user contracts, the user can connect to the IP network of the communication carrier and start a conversation from outside the home.
However, when the user tries to make an emergency call using the mobile phone and the like from outside the home, there may be cases that the access point of the communication carrier to which the user contracts does not exist around the location of the user, or even if the access point exists, it is difficult to start a conversation due to a low radio field strength. In such cases, the user cannot make the emergency call.